17 Jan
2024
17 Jan
'24
4:51 p.m.
pespin has submitted this change. (
https://gerrit.osmocom.org/c/osmo-ttcn3-hacks/+/35570?usp=email )
Change subject: mme: Add code to derive NAS token from NAS ul_count
......................................................................
mme: Add code to derive NAS token from NAS ul_count
NAS Token is derived from kasme and NAS ul_count as specified in 3GPP TS
33.401 A.9, and its LSB 16 bits passed to the network when mapping the GUTI to
RAI+PTMSI+PTIMSI_SIG.
Take the chance to move guti2rai_ptmsi() up to before the place it is
used.
Change-Id: I5e6003a2fe3e74cc93cfe4a288e6c114aa288d0b
---
M library/S1AP_Emulation.ttcn
M mme/LTE_CryptoFunctionDefs.cc
M mme/LTE_CryptoFunctions.ttcn
M mme/MME_Tests.ttcn
M mme/key_derivation.c
M mme/key_derivation.h
6 files changed, 100 insertions(+), 37 deletions(-)
Approvals:
Jenkins Builder: Verified
fixeria: Looks good to me, but someone else must approve
daniel: Looks good to me, approved
diff --git a/library/S1AP_Emulation.ttcn b/library/S1AP_Emulation.ttcn
index 1ef4a76..e3e3216 100644
--- a/library/S1AP_Emulation.ttcn
+++ b/library/S1AP_Emulation.ttcn
@@ -438,6 +438,7 @@
var S1APEM_Config s1cfg;
var charstring vlr_name, mme_name;
var integer ai;
+ var octetstring kasme;
alt {
/* Configuration primitive from client */
@@ -544,8 +545,13 @@
f_create_expect_proc(procedureCode, vc_conn);
S1AP_PROC.reply(S1APEM_register_proc:{procedureCode, vc_conn}) to vc_conn;
}
+ [] S1AP_PROC.getcall(S1APEM_derive_nas_token:{?, ?, -}) -> param(kasme, vc_conn) {
+ var integer assoc_id := f_assoc_id_by_comp(vc_conn);
+ var OCT32 nas_token := f_kdf_nas_token(kasme,
S1apAssociationTable[assoc_id].nus.tx_count)
+ S1apAssociationTable[assoc_id].nus.tx_count :=
S1apAssociationTable[assoc_id].nus.tx_count + 1;
+ S1AP_PROC.reply(S1APEM_derive_nas_token:{kasme, vc_conn, nas_token}) to vc_conn;
+ }
}
-
}
}
@@ -566,10 +572,12 @@
signature S1APEM_register(in MME_UE_S1AP_ID mme_id, in ENB_UE_S1AP_ID enb_id, in
S1AP_ConnHdlr hdlr);
signature S1APEM_register_proc(in integer procedureCode, in S1AP_ConnHdlr hdlr);
+signature S1APEM_derive_nas_token(in octetstring kasme, in S1AP_ConnHdlr hdlr, out OCT32
nas_token);
type port S1APEM_PROC_PT procedure {
inout S1APEM_register;
inout S1APEM_register_proc;
+ inout S1APEM_derive_nas_token;
} with { extension "internal" };
/* Function that can be used as create_cb and will use the expect table */
@@ -669,6 +677,17 @@
log(procedureCode);
}
+/* Derive NAS Token (and post-increment ul_count): */
+function f_s1apem_derive_nas_token(in octetstring kasme) runs on S1AP_ConnHdlr return
OCT32
+{
+ var OCT32 nas_token;
+ S1AP_PROC.call(S1APEM_derive_nas_token:{kasme, self, -}) {
+ [] S1AP_PROC.getreply(S1APEM_derive_nas_token:{kasme, self, ?}) -> param(nas_token)
{
+ return nas_token;
+ };
+ }
+}
+
private function f_expect_table_init()
runs on S1AP_Emulation_CT {
var integer i;
diff --git a/mme/LTE_CryptoFunctionDefs.cc b/mme/LTE_CryptoFunctionDefs.cc
index da2d521..7f82224 100644
--- a/mme/LTE_CryptoFunctionDefs.cc
+++ b/mme/LTE_CryptoFunctionDefs.cc
@@ -184,6 +184,14 @@
return OCTETSTRING(sizeof(kenb), kenb);
}
+OCTETSTRING f__kdf__nas__token(const OCTETSTRING &kasme, const INTEGER
&ul_count)
+{
+ TTCN_Buffer ttcn_buf_kasme(kasme);
+ uint8_t nas_token[32];
+
+ mme_kdf_nas_token(ttcn_buf_kasme.get_data(), (int)ul_count, nas_token);
+ return OCTETSTRING(sizeof(nas_token), nas_token);
+}
} // namespace
diff --git a/mme/LTE_CryptoFunctions.ttcn b/mme/LTE_CryptoFunctions.ttcn
index 18a3755..f0ea990 100644
--- a/mme/LTE_CryptoFunctions.ttcn
+++ b/mme/LTE_CryptoFunctions.ttcn
@@ -40,6 +40,8 @@
external function f_kdf_nh(in OCT16 kasme, in OCT32 sync_inp) return OCT32;
+external function f_kdf_nas_token(in OCT16 kasme, in integer ul_count) return OCT32;
+
/*********************************************************************************
* mid-level API
*********************************************************************************/
diff --git a/mme/MME_Tests.ttcn b/mme/MME_Tests.ttcn
index f4f41e2..50b89b3 100644
--- a/mme/MME_Tests.ttcn
+++ b/mme/MME_Tests.ttcn
@@ -83,6 +83,7 @@
hexstring imsi,
charstring ue_ip,
NAS_EPS_Types.GUTI guti optional,
+ octetstring kasme optional,
/* TEI (Control) local side, S11 (SGW) */
OCT4 s11_teic_local,
@@ -289,6 +290,7 @@
imsi := f_gen_imsi(imsi_suffix),
ue_ip := "192.168.123.50",
guti := omit,
+ kasme := omit,
s11_teic_local := '00000000'O,
s11_teic_remote := omit,
s5c_teic_local := '00000000'O,
@@ -585,11 +587,11 @@
const OCT3 plmn_id := '00F110'O;
const OCT6 sqn := '000000000020'O;
const OCT6 ak := substr(autn, 0, 6) xor4b sqn;
- var octetstring kasme := f_kdf_kasme(ck, ik, plmn_id, sqn, ak);
+ g_pars.ue_pars.kasme := f_kdf_kasme(ck, ik, plmn_id, sqn, ak);
var S1APEM_Config cfg := {
set_nas_keys := {
- k_nas_int := f_kdf_nas_int(1, kasme),
- k_nas_enc := f_kdf_nas_enc(1, kasme)
+ k_nas_int := f_kdf_nas_int(1, g_pars.ue_pars.kasme),
+ k_nas_enc := f_kdf_nas_enc(1, g_pars.ue_pars.kasme)
}
};
S1AP.send(cfg);
@@ -856,6 +858,31 @@
}
}
+
+/* 3GPP TS 23.401 D.3.5, TS 23.003 2.8.2.1 */
+private function guti2rai_ptmsi(in NAS_EPS_Types.GUTI guti, in OCT2 truncated_nas_token,
out RoutingAreaIdentity rai, out OCT4 ptmsi, out OCT3 ptmsi_sig) runs on ConnHdlr {
+ var bitstring mtmsi_bits := oct2bit(guti.mTMSI);
+ var bitstring ptmsi_bits;
+ var bitstring ptmsi_sig_bits;
+
+ rai := valueof(ts_RoutingAreaIdentity(guti.mccDigit1 & guti.mccDigit2 &
guti.mccDigit3,
+ guti.mncDigit3 & guti.mncDigit1 & guti.mncDigit2,
+ guti.mMEGI, guti.mMEC));
+ /* 3GPP TS 23.003 2.8.2.0: "P-TMSI shall be of 32 bits length where the two topmost
bits are
+ * reserved and always set to '11'. Hence, for a UE which may handover to
GERAN/UTRAN (based on
+ * subscription and UE capabilities), the corresponding bits in the M-TMSI are set to
'11'"
+ */
+ ptmsi_bits := '11'B & substr(mtmsi_bits, 2, 6) & oct2bit(guti.mMEC)
& substr(mtmsi_bits, 16, 16);
+ ptmsi_sig_bits := substr(mtmsi_bits, 8, 8) & oct2bit(truncated_nas_token);
+ ptmsi := bit2oct(ptmsi_bits);
+ ptmsi_sig := bit2oct(ptmsi_sig_bits);
+ /* TODO: The UE shall fill the remaining 2 octets of the <P-TMSI signature>
according to clauses 9.1.1, 9.4.1, 10.2.1, or
+ * 10.5.1 of 3GPP TS.33.401 [89] , as appropriate, for RAU/Attach procedures.*/
+}
+
+/* Test UE attached to EUTRAN reselecting a GERAN cell. In this scenario, the
+ * new SGSN will attempt to obtain information of the UE from the old SGSN (MME)
+ * through Gn interface using SGSN Context Request/Response procedure (OS#6294). */
private function f_gtp_sgsn_context_4g_to_2g(OCT4 new_sgsn_local_teid :=
'12345678'O) runs on ConnHdlr {
var template (value) GTPC_PDUs SGSNContextReqPDU;
var RoutingAreaIdentity rai;
@@ -864,7 +891,11 @@
var Gtp1cUnitdata gtpc_pdu;
var OCT4 old_mme_local_teid;
- guti2rai_ptmsi(g_pars.ue_pars.guti, rai, ptmsi, ptmsi_sig);
+ /* Derive NAS Token (and post-increment ul_count): */
+ var OCT32 nas_token := f_s1apem_derive_nas_token(g_pars.ue_pars.kasme);
+ var OCT2 truncated_nas_token := substr(nas_token, 30, 2);
+
+ guti2rai_ptmsi(g_pars.ue_pars.guti, truncated_nas_token, rai, ptmsi, ptmsi_sig);
SGSNContextReqPDU := ts_SGSNContextReqPDU(rai, new_sgsn_local_teid,
f_inet_addr(mp_gn_local_ip),
ptmsi := ts_PTMSI(ptmsi), ptmsi_sig := ts_PTMSI_sig(ptmsi_sig));
@@ -880,10 +911,10 @@
setverdict(pass);
}
[] GTP.receive {
- setverdict(fail, "unexpected GTPC message from MME");
+ Misc_Helpers.f_shutdown(__BFILE__, __LINE__, fail, log2str("unexpected GTPC
message from MME"));
}
[] T.timeout {
- setverdict(fail, "no SGSN Context Response from MME");
+ Misc_Helpers.f_shutdown(__BFILE__, __LINE__, fail, log2str("no SGSN Context
Response from MME"));
}
}
@@ -1312,36 +1343,6 @@
vc_conn.done;
}
-/* Test UE attached to EUTRAN reselecting a GERAN cell. In this scenario, the
- * new SGSN will attempt to obtain information of the UE from the old SGSN (MME)
- * through Gn interface using SGSN Context Request/Response procedure (OS#6294). */
-/* TS 23.003 2.8.2.1 */
-private function guti2rai_ptmsi(in NAS_EPS_Types.GUTI guti, out RoutingAreaIdentity rai,
out OCT4 ptmsi, out OCT3 ptmsi_sig) runs on ConnHdlr {
- var bitstring mtmsi_bits := oct2bit(guti.mTMSI);
- var bitstring ptmsi_bits;
- var bitstring ptmsi_sig_bits;
-
- rai := valueof(ts_RoutingAreaIdentity(guti.mccDigit1 & guti.mccDigit2 &
guti.mccDigit3,
- guti.mncDigit3 & guti.mncDigit1 & guti.mncDigit2,
- guti.mMEGI, guti.mMEC));
- /* 3GPP TS 23.003 2.8.2.0: "P-TMSI shall be of 32 bits length where the two topmost
bits are
- * reserved and always set to '11'. Hence, for a UE which may handover to
GERAN/UTRAN (based on
- * subscription and UE capabilities), the corresponding bits in the M-TMSI are set to
'11'"
- */
- ptmsi_bits := '11'B & substr(mtmsi_bits, 2, 6) & oct2bit(guti.mMEC)
& substr(mtmsi_bits, 16, 16);
- ptmsi_sig_bits := substr(mtmsi_bits, 8, 8) & oct2bit('0000'O);
- ptmsi := bit2oct(ptmsi_bits);
- ptmsi_sig := bit2oct(ptmsi_sig_bits);
- /* TODO: The UE shall fill the remaining 2 octets of the <P-TMSI signature>
according to clauses 9.1.1, 9.4.1, 10.2.1, or
- * 10.5.1 of 3GPP TS.33.401 [89] , as appropriate, for RAU/Attach procedures.*/
- /* TODO: 3GPP TS 33.401 9.1.1 The 16 least significant bits available in
- * the P-TMSI signature field shall be filled with the truncated NAS-token
- * according to 3GPP TS 23.003 [3].The truncated NAS-token is defined as the 16
- * least significant bits of the NAS-token.
- * The NAS-token is derived as specified in Annex A.9. The UE shall use the uplink NAS
COUNT value that it would use
- * in the next NAS message to calculate the NAS-token and increase the stored uplink NAS
COUNT value by 1.*/
- /* TODO: mMEC "also copied into the 8 Most Significant Bits of the NRI field within
the P-TMSI" */
-}
private function f_TC_ue_cell_reselect_eutran_to_geran(ConnHdlrPars pars) runs on
ConnHdlr {
f_init_handler(pars);
f_gtp_register_imsi(g_pars.ue_pars.imsi);
diff --git a/mme/key_derivation.c b/mme/key_derivation.c
index 36e4c91..8d5d8a4 100644
--- a/mme/key_derivation.c
+++ b/mme/key_derivation.c
@@ -80,3 +80,19 @@
gnutls_hmac_fast(GNUTLS_MAC_SHA256, k, 32, s, 14, kasme);
}
+
+/* TS33.401 Annex A.9: NAS token derivation for inter-RAT mobility */
+void mme_kdf_nas_token(const uint8_t *kasme, uint32_t ul_count, uint8_t *nas_token)
+{
+ uint8_t s[7];
+
+ s[0] = 0x17; /* FC Value */
+
+ ul_count = htonl(ul_count);
+ memcpy(s+1, &ul_count, 4);
+
+ s[5] = 0x00;
+ s[6] = 0x04;
+
+ gnutls_hmac_fast(GNUTLS_MAC_SHA256, kasme, 32, s, 7, nas_token);
+}
diff --git a/mme/key_derivation.h b/mme/key_derivation.h
index 496f52b..ae15b65 100644
--- a/mme/key_derivation.h
+++ b/mme/key_derivation.h
@@ -19,3 +19,5 @@
void mme_kdf_enb(const uint8_t *kasme, uint32_t ul_count, uint8_t *kenb);
void mme_kdf_nh(const uint8_t *kasme, const uint8_t *sync_input, uint8_t *kenb);
+
+void mme_kdf_nas_token(const uint8_t *kasme, uint32_t ul_count, uint8_t *nas_token);
--
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Gerrit-Project: osmo-ttcn3-hacks
Gerrit-Branch: master
Gerrit-Change-Id: I5e6003a2fe3e74cc93cfe4a288e6c114aa288d0b
Gerrit-Change-Number: 35570
Gerrit-PatchSet: 1
Gerrit-Owner: pespin <pespin(a)sysmocom.de>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: daniel <dwillmann(a)sysmocom.de>
Gerrit-Reviewer: fixeria <vyanitskiy(a)sysmocom.de>
Gerrit-Reviewer: pespin <pespin(a)sysmocom.de>
Gerrit-MessageType: merged